Ah very good. I wanted a nicer way to translate "а" than "and". I was going to propose "and in contrast", but that's a little wordy.
And if you hang around in Oxbridge circles you'll hear plenty of "whereas/ hence/ whence" and such other archaic conjugations. They are still very much in use in some parts of the English speaking world!
I do like whereas, BUT I'm not sure if "but" would be too strong a translation in all contexts. One example given in the T&N is "I like sleeping, and you don't." Clearly opposite preferences - although the second part doesn't negate the first per se.
There does not seem to be a conjunction offered here which would be translated "but". What does one use to connect two ideas when the second clearly contrasts or negates the first?
Polina, you need to join two independent clauses with a conjunction. I am a girl. (Independent clause.) He is a boy. (Independent clause.) I am a girl but/and/while/; he is a boy. Independent clauses can be a sentence on their own and will sound like it unless you add a conjunction where it's needed.